Merge pull request #24 from gnosis/update-1155-more

Update 1155 implementation to use 165 introspection interface
gnosis · Jun 8, 2019 · cf0d58f · cf0d58f
2 parents 11f545c + dfde885
commit cf0d58f
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Showing 4 changed files with 46 additions and 24 deletions.
diff --git a/contracts/ERC1155/ERC1155.sol b/contracts/ERC1155/ERC1155.sol
@@ -28,12 +28,12 @@ contract ERC1155 is ERC165, IERC1155
         public
     {
         _registerInterface(
-            this.safeTransferFrom.selector ^
-            this.safeBatchTransferFrom.selector ^
-            this.balanceOf.selector ^
-            this.balanceOfBatch.selector ^
-            this.setApprovalForAll.selector ^
-            this.isApprovedForAll.selector
+            ERC1155(0).safeTransferFrom.selector ^
+            ERC1155(0).safeBatchTransferFrom.selector ^
+            ERC1155(0).balanceOf.selector ^
+            ERC1155(0).balanceOfBatch.selector ^
+            ERC1155(0).setApprovalForAll.selector ^
+            ERC1155(0).isApprovedForAll.selector
         );
     }
 

diff --git a/contracts/ERC1155/ERC1155TokenReceiver.sol b/contracts/ERC1155/ERC1155TokenReceiver.sol
@@ -0,0 +1,13 @@
+pragma solidity ^0.5.0;
+
+import "./IERC1155TokenReceiver.sol";
+import "openzeppelin-solidity/contracts/introspection/ERC165.sol";
+
+contract ERC1155TokenReceiver is ERC165, IERC1155TokenReceiver {
+    constructor() public {
+        _registerInterface(
+            ERC1155TokenReceiver(0).onERC1155Received.selector ^
+            ERC1155TokenReceiver(0).onERC1155BatchReceived.selector
+        );
+    }
+}
diff --git a/contracts/ERC1155/IERC1155TokenReceiver.sol b/contracts/ERC1155/IERC1155TokenReceiver.sol
@@ -1,10 +1,13 @@
 pragma solidity ^0.5.0;
 
+import "openzeppelin-solidity/contracts/introspection/IERC165.sol";
+
 /**
-    @title ERC-1155 Multi Token Receiver
+    @title ERC-1155 Multi Token Receiver Interface
     @dev See https://eips.ethereum.org/EIPS/eip-1155
 */
-interface IERC1155TokenReceiver {
+contract IERC1155TokenReceiver is IERC165 {
+
     /**
         @dev Handles the receipt of a single ERC1155 token type. This function is
         called at the end of a `safeTransferFrom` after the balance has been updated.
@@ -46,12 +49,4 @@ interface IERC1155TokenReceiver {
         uint256[] calldata values,
         bytes calldata data
     ) external returns(bytes4);
-
-    /**
-        @dev Indicates whether a contract implements the `ERC1155TokenReceiver`
-        functions and so can accept ERC1155 token types. Will return
-        `bytes4(keccak256("isERC1155TokenReceiver()"))`
-        (i.e. 0x0d912442 or its own function selector).
-    */
-    function isERC1155TokenReceiver() external view returns (bytes4);
 }
diff --git a/contracts/PredictionMarketSystem.sol b/contracts/PredictionMarketSystem.sol
@@ -233,6 +233,22 @@ contract PredictionMarketSystem is OracleConsumer, ERC1155 {
         );
     }
 
+    // this value is meant to be used in a require(gasleft() >= CHECK_IS_RECEIVER_REQUIRED_GAS)
+    // statement preceding an ERC165 introspection staticcall to verify that a contract is
+    // an ERC1155TokenReceiver. Gas values gotten through experimenting with Remix.
+    uint constant CHECK_IS_RECEIVER_REQUIRED_GAS =
+        uint(10000) * 64 / 63 + 1 + // minimum gas required to exist before call opcode
+        700 +                       // call cost
+        564 +                       // cost for getting the stuff on the stack
+        100;                        // cost for executing require statement itself
+
+    bytes constant CHECK_IS_RECEIVER_CALLDATA = abi.encodeWithSignature(
+        "supportsInterface(bytes4)",
+        bytes4(keccak256("onERC1155Received(address,address,uint256,uint256,bytes)")) ^
+        bytes4(keccak256("onERC1155BatchReceived(address,address,uint256[],uint256[],bytes)"))
+    );
+
+
     function _doSafeTransferAcceptanceCheck(
         address operator,
         address from,
@@ -244,14 +260,13 @@ contract PredictionMarketSystem is OracleConsumer, ERC1155 {
         internal
     {
         if(to.isContract()) {
-            (bool callSucceeded, bytes memory callReturnData) = to.staticcall(
-                abi.encodeWithSignature("isERC1155TokenReceiver()")
-            );
+            require(gasleft() >= CHECK_IS_RECEIVER_REQUIRED_GAS, "ERC1155: not enough gas reserved for token receiver check");
+            (bool callSucceeded, bytes memory callReturnData) = to.call.gas(10000)(CHECK_IS_RECEIVER_CALLDATA);
 
             if(
                 callSucceeded &&
                 callReturnData.length > 0 &&
-                abi.decode(callReturnData, (bytes4)) == IERC1155TokenReceiver(to).isERC1155TokenReceiver.selector
+                abi.decode(callReturnData, (bool)) == true
             ) {
                 require(
                     IERC1155TokenReceiver(to).onERC1155Received(operator, from, id, value, data) ==
@@ -284,14 +299,13 @@ contract PredictionMarketSystem is OracleConsumer, ERC1155 {
         internal
     {
         if(to.isContract()) {
-            (bool callSucceeded, bytes memory callReturnData) = to.staticcall(
-                abi.encodeWithSignature("isERC1155TokenReceiver()")
-            );
+            require(gasleft() >= CHECK_IS_RECEIVER_REQUIRED_GAS, "ERC1155: not enough gas reserved for token receiver check");
+            (bool callSucceeded, bytes memory callReturnData) = to.staticcall.gas(10000)(CHECK_IS_RECEIVER_CALLDATA);
 
             if(
                 callSucceeded &&
                 callReturnData.length > 0 &&
-                abi.decode(callReturnData, (bytes4)) == IERC1155TokenReceiver(to).isERC1155TokenReceiver.selector
+                abi.decode(callReturnData, (bool)) == true
             ) {
                 require(
                     IERC1155TokenReceiver(to).onERC1155BatchReceived(operator, from, ids, values, data) ==